Field of the Invention
The present invention relates to a laser welding apparatus for spacer grid of nuclear fuel assembly, and more particularly to a laser welding apparatus enhancing serviceability.
Description of the Related Art
A nuclear reactor is equipment that is made to control nuclear fission artificially to generate energy, or to be used for various purposes such as production of radioisotope or plutonium, or radiation field formation, etc.
In general, light water reactor nuclear power plant uses enriched uranium in which ratio of uranium-235 is increased by 2 to 5%. For nuclear fuel to be used in nuclear reactors, fuel fabrication is processed in a way that cylindrical pellet hefting about 5 g is made of uranium. In order to manufacture a fuel rod, theses pellets come charging zircaloy cladding and spring and helium gas are put in and then an end plug is welded in a rod end. The fuel rods are charged in skeleton finally to form a fuel assembly and combusted by nuclear reaction in the nuclear reactor.
Spacer grid in nuclear fuel assembly which forms skeleton with a fuel rod, instrument tube, and guide tube, is made by dozens of spacer grid straps. Each spacer grid strap has a plurality of incision parts such as a slot. Spacer girds are placed longitudinally and laterally at regular interval so that spacer grid straps cross each other respectively. Thus incision parts are interconnected to each other by fitting to each other so that spacer grid forms grid space.
However these spacer grid straps are interconnected to each other by inserting into incision parts, spacer grid strap itself sways because of gaps in most incision parts. Thus the points of intersection where spacer grid straps cross each other cross parts, and parts in which connection is not solid such as outside, corner, etc. are welded in order to prevent spacer grids from swaying. Laser welding is mostly used for the welding method of spacer grid.
For example, the present applicant's Korean Patent No. 10-0922162 registered on 9 Oct. 2009 suggests a laser welding device for spacer grid of nuclear fuel assembly for enhancing workability and productivity.
The present inventor intends to improve further this conventional laser welding device for spacer gird of nuclear assembly.